1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same, and more specifically to a semiconductor device in which wiring is carried out in multilayered form, and a manufacturing method thereof.
2. Description of the Related Art
A highly integrated semiconductor device has been formed with wirings provided in multilayered form. The semiconductor device includes wirings provided in multilayered form with an interlayer insulating film low in dielectric constant interposed therebetween. The wirings of the respective layers are electrically connected to each other via a through hole defined in the interlayer insulating film. Such a conventional semiconductor device 200 will be explained using FIG. 10.
The semiconductor device 200 includes a semiconductor substrate 211 formed with an unillustrated semiconductor element, an insulating film 212 formed on the substrate 211, a high melting-point metal layer 213 formed on the insulating film 212, a lower wiring 216 made up of an aluminum alloy layer 214 made of aluminum and copper, which is formed on the high melting-point metal layer 213, and a cap metal layer 215 formed on the alloy layer 214, an interlayer insulating film 217 formed on the insulating film 212 so as to cover the lower wiring 216, a through hole 218 defined in the interlayer insulating film located on the lower wiring 216, an adhesion layer 219 provided within the through hole 218, a plug 220 formed within the through hole 218 in which the adhesion layer 219 is formed, and an upper wiring 221 electrically connected to the lower wiring 216.
A method of manufacturing the above-described conventional semiconductor device 200 will next be described.
An insulating film 212 is deposited on a semiconductor substrate 211 formed with an unillustrated semiconductor element. Thereafter, a layer of a high melting-point metal, which is obtained by laminating titanium nitride (TiN) and titanium (Ti), is formed on the insulating film 212. Afterwards, a layer of an aluminum alloy made of aluminum (Al) and copper (Cu) is formed on the high melting-point metal layer. Further, a laminated layer of titanium nitride and titanium, or a layer made of titanium alone is formed on the aluminum alloy layer as a layer of a cap metal. These high melting-point layer, aluminum alloy layer and a cap metal layer are patterned to predetermined shapes to form a lower wiring 216 comprising a high melting-point layer 213, an aluminum alloy layer 214 and a cap metal layer 215. After the formation of the lower wiring 216, an interlayer insulating film 217 is formed on the insulating film 212 so as to cover the lower wiring 216. Thereafter, a concave hole, which reaches from the surface on the interlayer insulating film 217 to the lower wiring 216, is formed as a through hole 218.
Afterwards, a cleaning process is effected on a bottom surface 222 of the through hole to remove a residual material developed upon formation of the through hole 218. Thereafter, an adhesion layer 219 using titanium nitride is formed on an inner wall of the through hole 218. A plug 220 using tungsten is formed within the through hole 218 in which the adhesion layer 219 is formed. After the formation of the plug 220, an upper wiring 221 is formed on the plug 220 by a process similar to that at the formation of the lower wiring 216.
In addition to the conventional semiconductor device 200, there is known a conventional semiconductor device wherein respective wirings of individual layers are electrically connected to each other without using different types of metals to thereby reduce resistance in a through hole (see Patent Document 1: Japanese Unexamined Patent Publication No. Hei 05-047940 (FIG. 1)).
Although an alloy made of aluminum, silicon and copper is formed as a plug within the through hole of the semiconductor device disclosed in the patent document 1, it is difficult to scale down or miniaturize the semiconductor device by use of the alloy in today when the diameter of the through hole, which is less than or equal to 0.5 μm, be in the mainstream. Accordingly, a plug using tungsten is formed in place of the above alloy nowadays.